The present invention relates to an oil-soluble dye which can be suitably used for inks for inkjet recording, inks for ball-point pens, inks for markers, toners, paints such as lacquers, inks for felt pens, and the like. The oil-soluble dye as referred to in the present specification means a non-water-soluble dye in general.
The present invention also relates to a water-based ink, and more particularly to a water-based ink which can be suitably used for a water-based ink for inkjet recording and the like.
Oil-soluble dyes have been used for various applications mentioned above by dissolving the oil-soluble dye in an organic solvent and the like; dispersing the oil-soluble dye in water; or containing the oil-soluble dye in a polymer and thereafter dispersing the polymer in water.
Various oil-soluble dyes hitherto have been developed. However, there has not yet been developed an oil-soluble dye which has vivid color tone, which is excellent in light fastness and weathering resistance, which has acid resistance and alkali resistance, and which is capable of sufficiently dissolving in an organic solvent.
For instance, as oil-soluble magenta dyes, there have been known monoazoic dyes such as C.I. Solvent Red 1, 3; disazoic dyes such as C.I. Solvent Red 18, 24, 27; metal complex dyes such as C.I. Solvent Red 8, 132; anthraquinone dyes such as C.I. Solvent Red 52, 111, 145, 146, 149, 150, 151, 155; xantene dyes such as C.I. Solvent Red 49, 218; amino ketone dyes such as C.I. Solvent Red 109, 179, 180; perinone dyes such as C.I. Solvent Red 135, 176; and the like. Among them, monoazoic dyes, disazoic dyes, metal complex dyes, anthraquinone dyes, amino ketone dyes and oil-soluble perinone dyes have some defects such that they have low solubility in an organic solvent having a low polarity, such as toluene, and dull color tones. Also, the oil-soluble xantene dye has poor light fastness.
As yellow dyes, azoic dyes such as C.I. Solvent Yellow 14, 16, 29, 33, 44, 56, 77, 79, 82, 93, 114, 116, 117 have been marketed, but all of those have some defects such that they have low solubility in an organic solvent having a low polarity, and poor handling ability. As cyanine dyes, metal phthalocyanine dyes, triphenylmethane dyes and anthraquinone dyes such as C.I. Solvent Blue 14, 25, 35, 38, 70, 83, 94, 105 have been known, but those cyanine dyes have the same defects as those of the yellow dyes.
In addition, a disperse dye having water resistance, acid resistance and alkali resistance generally has low solubility in an organic solvent.
On the other hand, water-soluble dyes such as acid dyes include ones having vivid color tone and being excellent in fastness. When this dye is neutralized with, for instance, a basic compound having high hydrophobicity such as octylamine, the neutralized dye would possess solubility in an organic solvent with maintaining characteristics as a dye. However, the neutralized dye is poor in acid resistance and alkali resistance.
A carbon black-dispersed ink has been partly used as a black ink employed in a water-based ink for personal or office printers, and the like, excluding the industrial uses. Water-soluble dyes are used for most of the black inks. Also, the water-soluble dyes have been the mainstream of color inks.
However, the water-based ink in which a water-based dye has been used has a defect that its water resistance is drastically lowered.
In order to improve water resistance, inks made of a pigment dispersion have been developed. However, the inks, particularly color inks are insufficient for dispersibility, and color tone for high color reproduction quality, optical density and reliability.
An object of the present invention is to provide an oil-soluble dye which is excellent in water rest alkali resistance, acid resistance, light fastness and solvent solubility.
Another object of the present invention is to provide a water-based ink which has vivid color tone, which imparts excellent water resistance, light fastness and weathering resistance to printed characters, ad which is excellent in storage stability.
A further object of the present invention is to provide a water-based ink for inkjet recording, which would not cause clogging on the printer heads.
These objects and other objects of the present invention will be apparent from the following description.
According to the present invention, there are provided:
(1) an oil-soluble dye prepared by subjecting a water-soluble dye having at least one group selected from the group consisting of sulfonate group and carboxyl group in its molecule to amidation;
(2) a water-based ink comprising an oil-soluble dye prepared by subjecting a water-soluble dye having at least one group selected from the group consisting of sulfonate group and carboxyl group in its molecule to amidation; and
(3) a process for preparing an oil-soluble dye, comprising halogenating a water-soluble dye having at least one group selected from the group consisting of sulfonate group and carboxyl group in its molecule, and thereafter subjecting the resulting halogenated water-soluble dye to amidation.
The water-soluble dye having at least one group selected from the group consisting of sulfonate group and carboxyl group in its molecule includes acid dyes, reactive dyes, direct dyes and food dyes, having at least one group selected from the group consisting of sulfonate group and carboxyl group in its molecule.
The acid dye includes, for instance,
C.I. Acid Yellow 1, 2, 5, 7, 16, 17, 23, 24, 26, 28, 29, 31, 41, 44, 48, 50, 51, 52, 52:1, 58, 60, 62, 63, 64, 67, 72, 76, 77, 94, 107, 108, 109, 110, 112, 115, 118, 119, 121, 122, 131, 132, 139, 140, 155, 156, 157, 158, 159, 172, 191, preferably C.I. Acid Yellow 5, 17, 23;
C.I. Acid Black 1, 3, 4, 7, 11, 12, 13, 14, 17, 18, 19, 23, 25, 29, 34, 36, 38, 39, 40, 41, 42, 44, 49, 50, 53, 55, 59, 61, 64, 70, 71, 72, 75, 76, 78, 79, 98, 99, 110, 111, 112, 114, 116, 118, 119, 122, 127, 128, 131, 135, 141, 142, 143, 151, 159, 161, 162, 163, 164, 165, 169, 172, 174, 190, 195, 196, 197, 199, 218, 219, 222, 227;
C.I. Acid Orange 7, 8, 10, 19, 20, 24, 28, 33, 41, 45, 51, 56, 64;
C.I. Acid Red 1, 4, 6, 8, 9, 13, 14, 15, 18, 19, 21, 26, 27, 30, 32, 34, 35, 37,40, 42, 44, 51, 52, 54, 57, 62, 75, 77, 80, 82, 83, 85, 87, 88, 89, 92, 94, 97, 106, 108, 110, 111, 114, 115, 117, 118, 119, 127, 128, 129, 130, 131, 133, 134, 135, 138, 143, 144, 145, 151, 152, 154, 155, 158, 168, 172, 176, 180, 183, 184, 186, 187, 194, 198, 199, 209, 211, 215, 216, 217, 219, 249, 252, 254, 256, 257, 261, 262, 263, 265, 266, 274, 276, 282, 283, 289, 299, 301, 305, 317, 318, 320, 321, 322, 336, 337, 361, 396, 397, preferably C.I. Acid Red 35, 37, 40, 52, 87, 92, 265, 289;
C.I. Acid Violet 5, 7, 11, 15, 34, 35, 41, 43, 47, 48, 49, 51, 75, 90, 103, 126;
C.I. Acid Blue 1, 7, 9, 15, 22, 23, 25, 27, 29, 40, 41, 43, 45, 51, 53, 54, 55, 56, 59, 60, 62, 72, 74, 76, 78, 80, 81, 82, 83, 90, 92, 93, 100, 102, 103, 104, 106, 111, 112, 113, 117, 120, 124, 126, 127, 129, 130, 131, 138, 140, 142, 143, 145, 151, 154, 158, 161, 166, 167, 168, 170, 171, 175, 181, 182, 183, 184, 187, 192, 199, 203, 204, 205, 207, 220, 221, 229, 230, 232, 234, 236, 247, 249, 258, 260, 264, 271, 277, 278, 279, 280, 288, 290, 326, preferably C.I. Acid Blue 9;
C.I. Acid Green 3, 9, 12, 16, 19, 20, 25, 27, 41, 44;
C.I. Acid Brown 4, 14, and the like.
The reactive dye includes, for instance,
C.I. Reactive Black 1, 3, 4, 5, 6, 8, 12, 14, 21, 23, 26, 31, 32, 34, 37, preferably C.I. Reactive Black 37;
C.I. Reactive Yellow 1, 2, 3, 12, 13, 14, 15, 17, 18, 23, 24, 25, 26, 27, 29, 35, 37, 41, 42;
C.I. Reactive Orange 2, 5, 7, 16, 20, 24;
C.I. Reactive Red 3, 6, 7, 11, 12, 13, 15, 17, 19, 21, 22, 23, 24, 29, 35, 36, 37, 40, 41, 42, 43, 45, 49, 55, 63, 66, 84, 120, 180, 184, preferably C.I. Reactive Red 23, 24, 120, 180;
C.I. Reactive Violet 1, 2, 3, 4, 5, 6, 7, 8, 9, 16, 17, 22, 23, 24, 26, 27, 33, 34;
C.I. Reactive Blue 2, 3, 5, 7, 8, 10, 12, 13, 14, 15, 17, 18, 19, 20, 21, 25, 26, 27, 28, 29, 37, 38, 40, 41;
C.I. Reactive Green 5, 7;
C.I. Reactive Brown 1, 7, 16, and the like.
The direct dye inch includes, for instance,
C.I. Direct Black 2, 4, 9, 11, 14, 17, 19, 22, 27, 32, 36, 38, 41, 48, 51, 56, 62, 69, 71, 74, 75, 77, 78, 80, 91, 94, 97, 105, 106, 107, 108, 112, 113, 114, 117, 118, 121, 122, 125, 132, 133, 146, 154, 166, 168, 171, 173, 194, 199;
C.I. Direct Yellow 1, 2, 4, 8, 9, 11, 12, 24, 26, 27, 28, 29, 33, 34, 35, 39, 41, 42, 44, 48, 50, 51, 53, 58, 59, 68, 72, 85, 86, 87, 88, 89, 93, 95, 96, 98, 100, 106, 108, 109, 110, 127, 130, 132, 135, 141, 142, 144, 161, 163, preferably C.I. Direct Yellow 86, 132;
C.I. Direct Orange 6, 8, 10, 26, 29, 39, 41, 49, 51, 62, 102;
C.I. Direct Red 1, 2, 4, 8, 9, 11, 13, 15, 17, 20, 23, 24, 26, 28, 31, 33, 37, 39, 44, 46, 47, 48, 51, 59, 62, 63, 72, 73, 75, 76, 77, 79, 80, 81, 83, 84, 85, 87, 89, 90, 92, 94, 95, 99, 101, 108, 110, 111, 113, 145, 173, 184, 189, 197, 201, 207, 211, 212, 214, 218, 220, 221, 223, 224, 225, 226, 227, 228, 229, 230, 232, 233, 240, 241, 242, 243, 247, 250, 256, 257, 321;
C.I. Direct Violet 1, 7, 9, 12, 35, 47, 48, 51, 66, 90, 93, 94, 95, 98, 100, 101;
C.I. Direct Blue 1, 2, 6, 8, 10, 12, 15, 22, 25, 34, 41, 55, 67, 68, 69, 70, 71, 72, 75, 76, 77, 78, 80, 81, 82, 83, 84, 86, 87, 90, 98, 106, 108, 109, 110, 120, 123, 151, 156, 158, 159, 160, 163, 165, 168, 189, 192, 193, 194, 195, 196, 199, 200, 201, 202, 203, 207, 211, 213, 214, 218, 225, 226, 229, 236, 237, 239, 244, 246, 248, 249, 251, 252, 258, 264, 270, 280, 287, 288, 289, 291, preferably C.I. Direct Blue 86, 199;
C.I. Direct Green 1, 6, 8, 28, 33, 37, 63, 64;
C.I. Direct Brown 1A, 2, 6, 25, 27, 44, 58, 95, 100, 101, 106, 112,173, 194, 195, 209, 210, 211, and the like.
The food dye includes, for instance,
C.I. Food Black 1, 2; C.I. Food Yellow 3, 4, 5; C.I. Food Red 2, 3, 7, 9, 14, 52, 87, 92, 94, 102, 104, 105, 106; C.I. Food Violet 2; C.I. Food Blue 1, 2; C.I. Food Green 2, 3, and the like.
Among them, C.I. Acid Red 289, C.I. Acid Yellow 23, C.I. Acid Yellow 17, C.I. Direct Yellow. 86 and C.I. Direct Yellow 132 are preferable, from the viewpoints of having excellent color reproduction quality, having vivid color tone, and being excellent in light fastness and weathering resistance.
The oil-soluble dye of the present invention can be prepared by subjecting sulfonate group and/or carboxyl group of the water-soluble dye to amidation. It is preferable that halogenation is carried out before the amidation. Among the halogenation, chlorination is more preferable.
The halogenation of the water-soluble dye can be carried out in an organic solvent. The organic solvent is not limited to specified ones, as long as the organic solvent can dissolve the water-soluble dye. The organic solvent includes halogen-containing solvents such as chloroform, methylene chloride and dichloroethane; aprotic solvents such as thionyl chloride, toluene, methyl ethyl ketone, 1,3-dimethyl-2-imidazohidinone and 2-pyrrolidone; and the like. Among them, 1,3-dimethyl-2-imidazoldinone and chloroform can be suitably used from the viewpoint of dye solubility, inertness to a halogenating agent, and costs. The amount of the organic solvent is not limited to specified ones, and it is preferable that the amount is usually 500 to 100000 parts by weight or so, based on 100 part by weight of the water-soluble dye.
When the water-soluble dye is halogenated, it is preferable to use a catalyst. The catalyst includes a dialkylformamide represented by the formula:
HCONR1R2
wherein each of R1 and R2 is independently an alkyl group having 1 to 5 carbon atoms; and the like. Among R1 and R2, methyl group and ethyl group are preferable, and methyl group is especially preferable. Among the catalyst, N,N-dimethylformamide can be suitably used.
It is desired at the amount of the catalyst is 0.001 to 100 mol, preferably 0.1 to 50 mol, more preferably 1 to 5 mol, per one mol of the water-soluble dye, from the viewpoints of reaction rate, yield, costs and the like and from the viewpoint of yield when isolation and purification are carried out by washing with water.
The halogenation of the water-soluble dye can be readily carried out by previously dissolving a water-soluble dye and a catalyst in an organic solvent, and adding a halogenating agent to the resulting water-soluble dye solution.
When the water-soluble dye is halogenated, it is preferable that the internal of the reaction system is previously replaced with an inert gas to provide an inert gas atmosphere. The inert gas includes nitrogen gas, argon gas, and the like. Among them, nitrogen gas is preferable.
It is desired that the temperature of the water-soluble dye solution is 0xc2x0 to 80xc2x0 C., preferably 0xc2x0 to 6xc2x0 C., more preferably 10xc2x0 to 40xc2x0 C. when the halogenating agent is added to the water-soluble dye solution, from the viewpoints of stability of reaction, safety and suppression of side reactions, and from the viewpoints of reaction rate, yield and costs, and the like.
The halogenating agent includes, for instance, thionyl chloride, chlorine gas, hydrochloric acid, phosphorus pentachloride, phosphonyl chloride, sulfonyl chloride, phosgene, and the like. Among them, thionyl chloride is preferable, from the viewpoints of reaction yield, safety and costs. It is preferable that the amount of the halogenating agent is an amount capable of sufficiently halogenating sulfonate group and/or carboxyl group existing in the water-soluble dye. It is preferable at the amount of the halogenating agent is usually 1 to 100 mol, per one mol of he total amount of the sulfonate group and the carboxyl group existing in the water-soluble dye.
After the addition of the halogenating agent, it is desired that the reaction mixture is aged at a temperature of 15xc2x0 to 85xc2x0 C., preferably 15xc2x0 C. to 35xc2x0 C. for 1 to 24 hours or so, in order to sufficiently progress the halogenation reaction. Also, the above-mentioned catalyst can be added to the reaction mixture as occasion demands, and the mixture can be further aged. After the halogenation reaction is sufficiently progressed, halogenating agent such as thionyl chloride is removed from the mixture by washing with water, and amidation can be carried out. The amidation can also be immediately carried out after the halogenation, without washing with water.
Next, the amidation of the halogenated water-soluble dye can be carried out by subsequently adding an amidation agent to the resulting reaction solution. It is preferable to use as the amidation agent a primary amine, a secondary amine, or a basic dye having an amino group in its molecule, from the viewpoints of solubility of the reaction product in a solvent, absorbance of the reaction product, and the like.
The amine includes a primary amine represented by the formula:
NH2R3
wherein R3 is an alkyl group having 8 to 24 carbon atoms, especially preferably 12 to 24 carbon atoms, an aryl group having 6 to 24 carbon atoms, a trialkylsilyl group having 3 to 14 carbon atoms, or a fluoroalkyl group having an alkyl group of 1 to 12 carbon atoms; and the like. It is preferable that the number of carbon atoms of the primary amine is not less than 6, from the viewpoint of non-water solubility. In addition, it is preferable to use the basic dye having an amino group in its molecule as an amidation agent, such as C.I. Basic Red 9, C.I. Basic Blue 5 or the like, from the viewpoint of the improvement of color development of the dye.
The secondary amine includes a secondary amine represented by the formula:
HNR4R5
wherein each of R4 and R5 is independently an alkyl group having 2 to 12 carbon atom preferably 4 to 10 carbon atoms, an aryl group having 6 to 10 carbon atoms, a trialkylsilyl group having 3 to 10 carbon atoms, a fluoroalkyl group having an alkyl group of 1 to 12 carbon atoms, or R4 may form a heterocyclic ring together with R5; and the like. The alkyl group having 2 to 12 carbon atoms, preferably 4 to 10 carbon atoms includes butyl group, pentyl group, hexyl group, n-octyl group, 2-ethylhexyl group, and the like. Among them, hexyl grow, n-octyl group and 2-ethylhexyl group are preferable. It is desirable that the number of carbon atoms is not more than 12, preferably not more than 10, because the absorbance is appropriate. Among the aryl groups having 6 to 10 carbon atoms, phenyl group, benzyl group, and the like are preferable. As the trialkylsilyl group having 3 to 10 carbon atoms, trimethylsilyl group is preferable. As the fluoroalkyl group, fluoromethyl group is preferable. In addition, when R4 forms a heterocyclic ring together with R5, it is preferable that the heterocyclic ring is 5-membered or 6-membered ring.
Among the amidation agents, a hexaalkyldisilazane represented by the formula: 
wherein each of Ra, Rb, Rc, Rd, Re and Rf is independently an alkyl group having 1 to 6 carbon atoms, represented by hexamethyldisilazane, dibutylamine, dioctylamine, dihexylamine and di-2-ethylhexylamine are preferable, from the viewpoints of solubility of the reaction product in a solvent, absorbance of the reaction product, and the like. Especially, di-2-ethylhexylamine is preferable. The secondary amine is preferable, because the non-water solubility of the reaction product sometimes becomes insufficient when the primary amine has too low a molecular weight, and alkali resistance and absorbance of the reaction product sometimes become insufficient when the primary amine has too high a molecular weight.
It is desired that the amount of the amidation agent is 1.2 to 20 mol, preferably 1.2 to 10 mol, per one mol of the total amount of the sulfonate group and the carboxyl group, from the viewpoints of reaction rate and yield and the viewpoint of yield during washing with water.
When the amidation agent is added, it is desired that the liquid temperature of the above-mentioned reaction solution is 0xc2x0 to 60xc2x0 C., preferably 10xc2x0 to 20xc2x0 C., from the viewpoints of reaction rate and yield and in consideration of the boiling points of the amidation agent and the solvent.
In addition, it is preferable that the atmosphere during the amidation is an inert gas atmosphere which is similar to that described above, from the viewpoint of stability of the reaction intermediate (halogenated product).
After the addition of the amidation agent the reaction mixture can be aged at a temperature of 20xc2x0 to 80xc2x0 C., preferably 20xc2x0 to 60xc2x0 C. for 1 to 24 hours or so in order to sufficiently progress the amidation.
The oil-soluble dye is thus obtained. The oil-soluble dye can be collected by washing the resulting reaction solution containing the oil-soluble dye with water, an aqueous alkali or the like allowing the oil-soluble dye to precipitate in hexane or the like, and filtering the precipitated oil-soluble dye. The oil-soluble dye can be dried or further washed, as occasion demands.
Among the oil-soluble dyes, it is preferable to use an oil-soluble dye having at least one group selected from the group consist of a group represented by xe2x80x94SO2NR4R5, wherein R4 and R5 are as defined above, and a group represented by xe2x80x94CONR4R5wherein R4 and R5 are as defined above.
In the water-soluble dye having at least one group selected firm the group consisting of sulfonate group and carboxyl group in its molecule, which can be suitably used in the present invention, each of C.I. Acid Red 289, C.I. Acid
Yellow 23, C.I. Acid Yellow 17 and C.I. Direct Yellow 132 corresponds to an oil-soluble dye represented by the formula (1): 
wherein each of R6 and R7 is independently xe2x80x94SO2NR4R5, wherein R4 and R5 are as defined above; an oil-soluble dye represented by the formula (II): 
wherein R6 and R7 are as defined above; and R8 is xe2x80x94CONR4R5 wherein and R5 are as defined above; an oil-soluble dye represented by the formula (III): 
wherein R6 and R7 are as defined above; and an oil-soluble dye represented by the formula (IV): 
wherein R8 is xe2x80x94SO2NR4R5, wherein R4 and R5 are as defined above, respectively. The oil-soluble dyes represented by the formulas (I) to (IV) can be those which are not prepared from a water-soluble dye.
Since the oil-soluble dye of the present invention is excellent in all of water resistance, alkali resistance, acid resistance, light fastness and solvent solubility as mentioned above, the oil-soluble dye can be suitably used for inks for inkjet recording, inks for ball-point pens, inks for markers, toners, paints such as lacquers, inks for felt pens, and the like.
The emulsion comprising an oil-soluble dye implies both of the following:
(I) a dispersion comprising an emulsion in which only an oil-soluble dye is dispersed; and
(II) a dispersion comprising an emulsion in which polymer particles containing an oil-soluble dye are dispersed.
Among those embodiments, the latter embodiment (II) is preferable from the viewpoints of dispersion stability and jetting stability.
The dispersion comprising an emulsion in which only an oil-soluble dye is dispersed is an aqueous dispersion in which an oil-soluble dye is dispersed in water by a dispersant or a surfactant, or an aqueous dispersion of an oil-soluble dye, to which a self-dispersibility treatment is conducted.
The polymer component used in the polymer emulsion comprising the oil-soluble dye includes polyester polymers, vinyl polymers, polyurethane polymers, polyamide polymers, and the like. Among them, the vinyl polymers are preferable. The vinyl polymer is preferably a polymer obtained by copolymerizing a monomer composition comprising:
(a) at least one vinyl monomer selected from the group consisting of acrylic acid esters, methacrylic acid esters and styrenic monomers,
(b) a polymerizable unsaturated monomer having a salt-forming group, and
(c) a monomer copolymerizable with the vinyl monomer and the polymerizable unsaturated monomer having a salt-forming group.
The vinyl monomer includes acrylates such as methyl acrylate, ethyl acrylate isopropyl acrylate, n-butyl acrylate, t-butyl acrylate, isobutyl acrylate, n-amyl acrylate, n-hexyl acrylate, n-octyl acrylate and dodecyl acrylate; methacrylates such as methyl methacrylate, isopropyl methacrylate, n-butyl methacrylate, t-butyl methacrylate, isobutyl methacrylate, n-amyl methacrylate, 2-ethylhexyl methacrylate, lauryl methylate and polyethylene glycol methacrylate; and styrenic monomers such as styrene, vinyltoluene and 2-methylstyrene.
The polymerizable unsaturated monomer having a salt-forming group includes cationic monomers having a salt-forming group and anionic monomers having a salt-forming group.
The cationic monomer having a salt-forming group includes unsaturated tertiary amine-containing monomers, unsaturated ammonium salt-containing monomers, and the like. Among them, preferable examples include N,N-diethylaminoethyl acrylate, N-(Nxe2x80x2,Nxe2x80x2-dimethylaminoethyl) acrylamide, vinylpyridine, 2-methyl-5-vinylpyridine, dimethylaminoethyl methacrylate, dimethylaminoethyl methacrylate, and the like.
The anionic monomer having a salt-forming group includes unsaturated carboxylic acid monomers, unsaturated sulfonic acid monomers, unsaturated phosphoric acid monomers, and the like. Among them, preferable examples include acrylic acid, methacrylic acid, itaconic acid, maleic acid, fumaric acid, and the like.
The monomer copolymerizable with the vinyl monomer and the polymerizable unsaturated monomer having a salt-forming group includes acrylamide monomers; methacrylamide monomers; silicone macromers having a polymerizable functional group at one end; methacrylate macromers having a polymerizable functional group at one end; styrenic macromers having a polymerizable functional group at one end; polyester macromers having a polymerizable functional group at one end; polyurethane macromers having a polymerizable functional group at one end; polyalkyl ether macromers having a polymerizable functional group at one end; hydroxyl group-containing monomers; a monomer represented by the formula (V):
CH2xe2x95x90C(R7)COO(R8O)pR9xe2x80x83xe2x80x83(V)
wherein R7 is hydrogen atom or a lower alkyl group having 1 to 4 carbon atoms; R8 is a divalent hydrocarbon group having 1 to 30 carbon atoms which may have a hetero-atom; R9 is a monovalent hydrocarbon group having 1 to 30 carbon atoms which may have a hetero-atom; and p is a number of 1 to 60; and the like. Those monomers can be used alone or in admixture of at least two kinds. Those monomers are given by way of exemplification, without intending to limit the present invention to those exemplified ones.
The hydroxyl group-containing monomer includes 2-hydroxyethyl acrylate, 3-hydroxypropyl acrylate, polyethylene glycol(n=2-30) acrylate, 2-hydroxyethyl methacrylate, 3-hydroxypropyl methacrylate, polyethylene glycol(n=2-30) methacrylate, poly(ethylene glycol(n=1-15).propylene glycol(n=1-15)) acrylate, poly(ethylene glycol(n=1-15).propylene glycol(n=1-15)) methacrylate, and the like. Among them, 2-hydroxyethyl acrylate and 2-hydroxyethyl methacrylate are preferable.
The monomer represented by the formula (V) exhibits excellent effects such that the jetting stability of the water-based ink of the present invention is increased, and that generation of crookedness is suppressed even when subjected to continuous printing.
Concrete examples of the monomer represented by the formula (V) include methoxypoloyethylene glycol (1-30, showing the value of p in the formula (V), hereinafter referred to the same) (meth)acrylates, methoxypolytetramethylene glycol (1-30) (meth)acrylates, ethoxypolyethylene glycol (1-30) (meth)acrylates,(iso)propoxypolyethylene glycol (1-30) (meth)acrylates, butoxypolyethylene glycol (1-30) (meth)acrylates, methoxypolypropylene glycol (1-30) (meth)acrylates, methoxy(ethylene glycol-propylene glycol copolymer) (1-30, out of which ethylene glycol: 1-29) (meth)acrylates, and the like. Those monomers can be used alone or in admixture of at least two kinds. Among them, methoxypolyethylene glycol (1-30) (meth)acrylates are preferable. The term xe2x80x9c(meth)acrylicxe2x80x9d as referred to in the present specification is intended to mean methacrylic or acrylic. Also, the term xe2x80x9c(iso)propoxyxe2x80x9d is intended to mean n-propoxy or isopropoxy.
Among those copolymerizable monomers, the silicone macromer, methacrylic acid ester macromer and the styrenic macromer are preferable.
It is desired that the content of the vinyl monomer in the monomer composition is 1 to 40% by weight, preferably 2 to 20% by weight, from the viewpoints of improvement in dispersion stability of the polymer emulsion and avoidance of scorching on the inkjet printer head.
It is desired that the content of the polymerizable unsaturated monomer having a salt-forming group in the monomer composition is 2 to 40% by weight, preferably 5 to 20% by weight, from the viewpoints of improvement in dispersion stability of the polymer emulsion and avoidance of scorching on the inkjet printer head.
It is desired that the content of the vinyl monomer and the monomer copolymerizable with the polymerizable unsaturated monomer having a salt-forming group in the monomer composition is 60 to 90% by weight, preferably 70 to 85% by weight, from the viewpoints of improvement in dispersion stability of the polymer emulsion and avoidance of scorching on the inkjet printer head.
The monomer composition may further comprise a polymerization chain transfer agent as occasion demands.
The polymer can be obtained by copolymerizing the monomer composition by a known polymerization method such as a bulk polymerization method, a solution polymerization method, a suspension polymerization method or an emulsion polymerization on method. Among those methods, the solution polymerization method is especially preferable.
The solvent used in the solution polymerization method includes aliphatic alcohols such as ethanol and propanol; ketones such as acetone and methyl ethyl ketone; esters such as ethyl acetate; aromatic solvents such as benzene and toluene; and the like. Those solvents can be used alone or in admixture of at least two kinds.
It is preferable that the weight-average molecular weight of the polymer is 3000 to 100000, preferably 3000 to 50000, as determined in accordance with gel permeation chromatography described in Examples. 6 to 10 and Comparative Examples 16 to 22 given below, from the viewpoint of avoidance of scorching on a printer head, and from the viewpoints of durability of print and stability of the dispersion.
In order to contain the oil-soluble dye in the polymer particles included in the emulsion, a known emulsification method such as a forced emulsification method, a phase-inversion emulsification method, a dispersion polymerization method or an emulsion polymerization method can be employed. Among them, the forced emulsification is preferable.
It is desired that the amount of the oil-soluble dye in the polymer emulsion is 5 to 900 parts by weight, preferably 10 to 400 parts by weight, based on 100 parts by weight of the solid matters of the polymer, from the viewpoints of optical density and easiness for incorporation of the dye in the fine polymer particles.
In addition, it is desired that the content of the solid matters contained in the polymer emulsion in the water-based ink is 0.5 to 30% by weight, preferably 1 to 20% by weight, from the viewpoints of jetting stability and optical density.
It is preferable that the average particle diameter of the oil-soluble dye-containing polymer particles contained in the polymer emulsion is 20 to 200 mm, from the viewpoint of dispersing stability.
When using a polymer emulsion in which a polymer being copolymerized with an anionic monomer is employed, it is preferable to add an anionic surfactant or an amphoteric surfactant to the polymer emulsion, in order to maintain the dispersion stability of a water-based ink. On the other hand, when using a polymer emulsion in which a polymer being copolymerized with a cationic monomer is employed, it is preferable to use a cationic surfactant or an amphoteric surfactant, in order to maintain the dispersion stability of the water-based ink.
The water-based ink of the present invention may contain a moisturizing agent as occasion demands.
The moisturizing agent includes, for instance, glycols such as ethylene glycol, propylene glycol, diethylene glycol, triethylene glycol and glycerol; and nitrogen-containing compounds, e.g. amino acids and the like, and urea, ethyleneurea, 2-pyrrolidone, N-methyl-2-pyrrolidone, 1,3-dimethylimidazolidinone, formamide, trimethylglycine, methylglycine and 6-amino-n-caproic acid. Those moisturizing agents can be used alone or in admixture of at least two kinds.
The water-based ink may further contain an additive such as a defoaming agent, a pH adjusting agent, an antiseptic, an ultraviolet ray absorbent, an oxygen absorbing agent, a chelating agent, as occasion demands, within a range which would not hinder the object of the present invention.